I add constraint with '>=' but in the model it is <= 0

I add some linear constr to the gurobi LP model as follow:

""" constraint (2)"""
for t in range(1, data.round_num + 1):
for p in range(1, data.parklot_num + 1):
con_name_2 = f'cons_(2)_{t}_{p}'
self.cons_RMP[con_name_2] = self.RMP.addConstr(sum(constrain_coef[f'{v}_{lot}_cons_2'][f'{t}_{p}']
* self.x[f'x_{v}_{lot}'] for v in
range(1, data.vehicle_num + 1) for lot in
range(1, data.parklot_num + 1))
<= 1, name=con_name_2)
""" constraint (3)"""
for t in range(2, data.round_num + 1):
for p in range(1, data.parklot_num + 1):
for q in range(1, data.parklot_num + 1):
if self.data.C[p - 1][q - 1] == 1:
con_name_3 = f'cons_(3)_{t}_{p}_{q}'
self.cons_RMP[con_name_3] = self.RMP.addConstr(
sum(constrain_coef[f'{v}_{lot}_cons_3'][f'{t}_{p}_{q}']
* self.x[f'x_{v}_{lot}'] for v in range(1, data.vehicle_num + 1) for lot in
range(1, data.parklot_num + 1))
>= data.C[p - 1][q - 1] - 2, name=con_name_3)
""" constraint (4)"""
for t in range(2, data.round_num + 1):
for p in range(1, data.parklot_num + 1):
for q in range(1, data.parklot_num + 1):
if self.data.C[p - 1][q - 1] == 1:
con_name_4 = f'cons_(4)_{t}_{p}_{q}'
self.cons_RMP[con_name_4] = self.RMP.addConstr(
sum(constrain_coef[f'{v}_{lot}_cons_4'][f'{t}_{p}_{q}']
* self.x[f'x_{v}_{lot}'] for v in range(1, data.vehicle_num + 1) for lot in
range(1, data.parklot_num + 1))
>= data.C[p - 1][q - 1] - 2, name=con_name_4)

""" constraint (5)"""
for t in range(1, data.round_num + 1):
con_name_5 = f'cons_(5)_{t}'
self.cons_RMP[con_name_5] = self.RMP.addConstr(sum(constrain_coef[f'{v}_{lot}_cons_5'][f'{t}']
* self.x[f'x_{v}_{lot}'] for v in
range(1, data.vehicle_num + 1) for lot in
range(1, data.parklot_num + 1))
== sum(data.In[k - 1, t - 1] for k in
range(1, data.vehicle_num + 1)), name=con_name_5)
""" constraint (6)"""
for t in range(1, data.round_num + 1):
for p in range(1, data.parklot_num + 1):
for q in range(1, data.parklot_num + 1):
if self.data.C[p - 1][q - 1] == 1:
con_name_6 = f'cons_(6)_{t}_{p}_{q}'
lhs = sum(constrain_coef[f'{v}_{lot}_cons_6'][f'{t}_{p}_{q}']
for v in range(1, data.vehicle_num + 1)
for lot in range(1, data.parklot_num + 1))
self.cons_RMP[con_name_6] = self.RMP.addConstr(lhs >= 0, name=con_name_6)

the model is output by the "write" function. I find for constrain(2)-(5), the operators are the same as I build, but for constraint(6), the operators are all <= 0, I have taken a part of it for reference.

cons_(6)_1_13_1: x_1 <= 0
cons_(6)_1_13_2: <= 0
cons_(6)_1_13_7: <= 0
cons_(6)_1_13_8: <= 0
cons_(6)_1_14_1: x_1 <= 0
cons_(6)_1_14_2: <= 0
cons_(6)_1_14_7: <= 0
cons_(6)_1_14_8: <= 0
cons_(6)_1_15_2: <= 0
cons_(6)_1_15_3: <= 0
cons_(6)_1_15_4: <= 0
cons_(6)_1_15_7: <= 0
cons_(6)_1_15_8: <= 0
cons_(6)_1_15_9: <= 0
cons_(6)_1_15_10: <= 0
cons_(6)_1_15_13: <= 0
cons_(6)_1_16_1: x_1 <= 0

David Torres Sanchez

Gurobi Staff

June 14, 2024 10:31
Edited

Hi Zichun,

Are the constraints the same?
Terms are sometimes re-arranged for an equivalent constraint.

Cheers,
David

Sian Hallsworth

August 09, 2024 16:41

Hi, I experience the same issue for example:

Constraint

x_Block.x_constraints.add( expr= x_Block.weight[h, n, n2] >= 0)

Computed IIS with flipped inequality sign in constraint

Minimize
 
Subject To
 R6193:
   x_Block.weight[3,0.0666740748972108,0.0666740748972108]
   <= 0
Bounds
 x_Block.weight[3,0.0666740748972108,0.0666740748972108] >= 0.0113540901668842
End

Riley Clement

August 10, 2024 00:29

Hi Sian,

Can you write out the LP file and find constraint R6193?

- Riley

I add constraint with '>=' but in the model it is <= 0

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